Vinylsulphone hardener

ABSTRACT

A vinylsulphone compound of the formula ##STR1## is provided. This compound is useful as cross-linking agent for hydrophilic colloids, especially for gelatin which is in the form of layers of photographic materials.

This application is a divisional of prior application Ser. No. 734,782,filed Oct. 22, 1976, and now U.S. Pat. No. 4,088,648.

This invention relates to a novel vinylsulphone compound, to itsproduction and to its use as a cross-linking agent for hydrophiliccolloids.

According to the present invention there is provided a vinylsulphonecompound of the formula ##STR2## The compound of formula (1) is preparedby reacting 2 molar proportions of 3-(2-chloroethylsulphonyl)-propionylchloride with 1 molar proportion of piperazine in a basic organicsolution to produce the compound of the formula ##STR3## AND THENDEHYDROCHLORINATING THIS COMPOUND TO PRODUCE THE COMPOUND OF FORMULA(1).

Chloroethylsulphonyl compounds may be dehydrochlorinated to thecorresponding vinylsulphonyl compounds in a number of different wayswhich are well known. An example of such a conversion is given in USP 3868 257 wherein triethylamine is used.

3-(2-Chloroethylsulphonyl)-propionic acid may be prepared by the methoddescribed in French patent specification No. 1363046 wherein2-chloroethylsulphinic acid is reacted with acrylic acid and3-(2-chloroethylsulphonyl)-propionyl chloride may be prepared therefromby reaction with thionyl chloride.

The vinylsulphone compound of formula (1) is of particular use incross-linking hydrophilic colloids.

Therefore according to another aspect of the present invention there isprovided a process for cross-linking hydrophilic colloids which containamino, imino and/or hydroxyl groups characterised in that the compoundof the formula (1) is incorporated into the colloid to effectcross-linking thereof.

The cross-linking process of the present invention can be used in thetextile and leather industry, the manufacture of paper and the plastics,glue and gelatin industry. Above all, it can be used as a process forhardening water-soluble colloids for example polyvinyl alcohol, gelatinor gelatin derivatives, especially when these colloids are in the formof layers in photographic materials. The reaction of these colloids withthe vinylsulphone compound of use in the present invention in generaltakes place easily, and in the usual manner. The vinylsulphone compoundis water-soluble and thus can be used as an aqueous solution.

In most cases in order to carry out the cross-linking process of thepresent invention it suffices to add the vinylsulphone compound of thepresent invention as an aqueous solution or in a solid form which is asfinely divided as possible, to an aqueous solution of the hydrophiliccolloid, with good stirring.

Thus, a solution of the vinylsulphone cross-linking agent in water, ormixed with, for example, ethanol, methanol or acetone, can be broughttogether with the colloids at normal or slightly raised temperature.Gelatin, which optionally may contain silver halide and/or othercomponents required to produce photographic images, has provedparticularly suitable for cross-linking by the process of the presentinvention.

The coating solution which is an aqueous solution containing bothgelatin and the vinylsulphone cross-linking agent can, in the usual way,be coated on a substrate to form a layer, and be dried. The layer canthen be left at elevated temperature or at room temperature for acertain time, for example up to 24 hours. Thereupon cross-linking, whichis evidenced by hardening of the layer, takes place rapidly andprogressively this is shown by the melting point of the gelatin beingraised substantially, for example from 25 to 60° C., and by thereciprocal swelling factor increase.

The amount of the vinylsulphone cross-linking agent used depends on thedesired degree of hardening of the gelatin layer required but issuitably from 0.1 to 10 percent by weight based on the weight of the drygelatin.

A particular advantage of the process of the present invention is thatwhen the vinylsulphone cross-linking agent is used at a lowconcentration it imparts a sufficient degree of hardness to the gelatinlayers in 18 to 24 hours, so that the coated material can be tested byprocessing a sample immediately following its manufacture, even if thetest be carried out at a raised temperature or in strong processingbaths.

It is a further advantage that during the process of the presentinvention, no significant change in pH of the gelatin layer occurs.

The cross-linking or hardening effect itself is very stable; even afterprolonged storage at room temperatures around 40° C. and at a relativeatmospheric humidity of about 70%, the reciprocal swelling factorremains above 0.2 (compare the Table in Example II)

Further the degree of hardening is also not changed significantly byacids or bases even on prolonged action, which indicates that thehardener-gelatin bond created has great resistance to hydrolysis.

The vinylsulphone compound of the present invention is furthermoregenerally sufficiently soluble in water and sufficiently stable inaqueous solutions to enable the process of the present invention to beused in the preparation of photographic material. Thus, for example itis particularly desirable - for the continuous manufacture ofphotographic materials - that batches of solutions of cross-linkingagents should remain stable at room temperature for several hours ordays and that the concentration should not decrease or should only do soinsignificantly. Also it is important that in the coating solution, atabout 40° C., the hardener should undergo very little or nodecomposition and very little or no reaction with water during therequisite standing time and dwell time, so as to maintain its fullcross-linking action over the course of several hours, during coating,drying and storage of the photographic material.

Furthermore, the viscosity of the coating solution should notsignificantly increase during the standing time as a result of theaddition of the hardener. It is also particularly important that even onprolonged treatment of the coated layer at raised temperature andatmospheric humidity conditions the hardener should not cause anyyellowing, fogging of photographic material or effect the contrastgraduation of the material on development.

The vinylsulphone compound of the present invention fulfils the abovedesiderata very well.

In particular it hydrolyses very little when present in an aqueoussolution. It does not discolour gelatin. When this compound is added toa gelatin solution it causes only a small increase in the viscosity ofthe solution and thus such solution can be coated without difficulty.The compound has a good hardening effect over a wide pH range and thuscan be used in the preparation of a wide range of photographicmaterials. This is shown in Example I which follows.

Thus the process of the present invention is suitable for hardening(cross-linking) all the layers in photographic material containinggelatin for example, intermediate layers, emulsion layers, base layers,top layers, backing layers and anti-halation layers. The layers cancontain not only the cross-linking agents but also additives of the mostdiverse kind for example, silver halide, pigments, such as bariumsulphate, titanium dioxide or silicon dioxide or those of organicnature, such as coloured pigments, and also image dyestuffs, colourcoupling agents, latices, sensitisers, filter dyestuffs, anti-halationdyestuffs and light screening dyestuffs, emulsion stabilisers, UVabsorbers, optical brighteners and even other crosslinking agents.

The present invention not only includes the novel vinylsulphone offormula (1), the process for preparing this compound, the process forcross-linking hydrophilic colloids using the vinylsulphone of formula(1) but also includes hydrophilic colloids cross-linked by the abovecross-linking process and in particular includes layers containinggelatin so cross-linked especially gelatine silver halide emulsionlayers and other layers in photographic material as well as thephotographic material containing such layers.

The following Example I shows the preparation of the vinylsulphonecompound of formula (1) and Example II shows the use of this compound incross-linking gelatin, a hydrophilic colloid.

EXAMPLE I

8.76 g 3-(2-chloroethylsulphonyl)-propionyl chloride was dissolved in100 ml dry dichloroethane. A solution of 1.72 g anhydrous piperazine and4.04 g triethylamine in 60 ml of dichlorethane was added dropwise at 10°to 15° C. over 1/2 hour. The mixture was stirred for a further 11/2hours at 10° to 15° C. then cooled in ice and filtered. The solid waswashed with dichloroethane, dried and then recrystallised fromethanol/water. Yield 6.2 g. Melting point: 188° to 189° C.

6.12 g of the above product was suspended in a mixture of 100 ml ethanoland 30 ml water at 50° C. 2.83 g triethylamine was added and the mixturestirred for 1 hour at 50° C. The solution was filtered and the filtrateevaporated under reduced pressure. The residue was recrystallised fromethanol. Yield 3.4 g. Melting point: 175° to 180° C.

EXAMPLE II

In the Example which follows, the reciprocal swelling factor is used asa measure of the hardening. The samples were prepared as follows:

6 ml of a 3% strength gelatine solution, 1 ml of a 1% strength dyestuffsolution of the formula ##STR4## 1 ml of 25 × 10⁻³ molar solution of thevinylsulphone as prepared in Example I and 5 ml of deionised water aremixed and the pH adjusted to 4.5 to 7.5. The solution is coated on a 13× 18 cm triacetate film. After solidification at 10° C., the layer isdried over the course of 2 hours at approx 20° C. (The dyestuff merelyserves to make the samples more readily visible during the swellingmeasurements). Some samples of the coated film were stored under roomconditions (NK, approx. 20° C., 50% relative atmospheric humidity) andother samples were incubated (CL, 43° C., 69% relative atmospherichumidity).

To determine the reciprocal swelling factor, a thin section of approx.20 μ is prepared from each of the samples and measured under amicroscope. The thickness of the dry gelatin layer is then determined,deionised water is then added and after 4 minutes the thickness of theswollen gelatin layer is measured. The reciprocal swelling factor 1/SFcorresponds to the following ratio: ##EQU1## The results of the coatingsare shown in the table below:

                  Table                                                           ______________________________________                                                   1/SF                                                               Coating pH                                                                            Storage  1 day    2 days 7 days 14 days                               ______________________________________                                        4.5     NK       0.060    0.077  0.109  0.200                                         CL       --       0.199  0.244  0.289                                 5.5     NK       0.114    0.164  0.236  0.323                                         CL       --       0.263  0.323  0.309                                 6.5     NK       0.188    0.218  0.272  0.350                                         CL       --       0.300  0.350  0.370                                 7.5     NK       0.222    0.242  0.285  0.360                                         CL       --       0.325  0.349  0.369                                 ______________________________________                                    

I claim:
 1. A process for cross-linking hydrophilic colloids whichcontain amino, imino and/or hydroxyl groups characterised in that thevinylsulphone compound of ##STR5## is incorporated into the colloid toeffect cross-linking thereof.
 2. A process according to claim 1 whereinthe hydrophilic colloid is polyvinyl alcohol, gelatin or a gelatinderivative.
 3. A process according to claim 2 wherein the polyvinylalcohol, gelatin or gelatin derivative is in the form of a layer inphotographic material or is used to form a layer in photographicmaterial.
 4. A process according to claim 3 wherein the gelatin layer isa gelatino silver halide emulsion layer.
 5. A process according to claim4 wherein the amount of vinylsulphone compound is from 0.1 to 10 percentby weight on the weight of the dry gelatin in the layer.
 6. Across-linked hydrophilic colloid which has been cross-linked by theprocess according to claim
 1. 7. A layer in a photographic materialcomprising cross-linked polyvinyl alcohol, gelatin or gelatinderivatives which has been cross-linked by the process according toclaim
 2. 8. A hardened gelatino silver halide emulsion layer inphotographic material which has been cross-linked by the processaccording to claim
 4. 9. Photographic material which contains at leastone layer according to claim
 7. 10. Photographic material which containsat least one layer according to claim 8.